According to media reports, Vilsack told the group that he'd warned Slaughter against banning antibiotics in animal agriculture. The secretary added that "the USDA's public position is, and always has been, that antibiotics need to be used judiciously, and we believe they already are."

The lawmakers say Vilsack mischaracterized both their legislation and the position of his own department.

"We hope that you can provide us with reassurances that your off-the-cuff remarks were taken out of context, and that you remain committed to protecting human and animal health," the two lawmakers wrote in a letter obtained by The Hill.

The lawmakers point out that their legislation — the Preservation of Antibiotics for Medical Treatment Act — does not ban antibiotics in animal agriculture but phases out seven antibiotics "critical in human medicine" from non-therapeutic uses in livestock production.

"We share your belief banning all uses of antibiotics would be counterproductive," they wrote.

The letter also points out that the USDA's Chief Veterinary Officer, John Clifford, testified before the House Energy and Commerce Committee in July that "USDA believes that it is likely that the use of antibiotics in animal agriculture does lead to some cases of antibacterial resistance among humans." Clifford added that the USDA is "committed to identifying opportunities to reduce usage and maintain the effectiveness of these drugs."

"Dr. Clifford's statements clearly indicate significant concern over this issue," the lawmakers said, "so we hope that you will clarify your comment on the subject."